Resistance set.



I. vB. SMITH.

RESISTANCE SET.

APPLICATION rILED 1112.12, 1913.

Patented July 28, 1914.

2 sums-SHEET 1 FG Ffiz THE NORRIS PETERS CU. FHOTOLITHO, WASHINGTON D L I. B. SMITH.

RESISTANCE SET.

APPLIGATION FILED MAR.

Patented July 28, 1914.

2 SHEETS-SHEET 2.

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q/viueomm Swewpmy mj@ VN#V NORMIS Iz-J'rnks U0. PNOTOJJTHO, WASHINGTON4 D C i' citizen of the United States, residing in UNTTED sTATEs PATENT OFFICE;

IRVING B. SMITH, AMBLER, PENNSYLVANIA, ASSIGNOR TO THE LEEDS &

NORTHRUP COMPANY, OF PHILADELPHIA, PENNSYLVANIA, A CORPORA- TION OF PENNSYLVANIA.

RESISTANCE SET.

T0 all whom it may concern:

Be it known that I, IRVING. B. SMITH, a

Ambler, State of Pennsylvania, have inventedl certain new and useful Improve ments in'Resistance Sets, of which the following is a specification.

My invention relates to resistance sets, such as decade sets, whereby various amounts of resistance, of preferably lmown values` may -be introduced into an electrical circuit for any purpose, particularly for electrical measurements.

Itis the object of my apparatus to provide resistance apparatus of this character which shallroccupyvsmall'spaoe, and which shall effect an economy in number of parts, in cost of parts, in manufacture andassembly, and which shall insure minimum error arising from variations of contact resistance or connecting leads. v

With these objects in"view mv invention resides 'in the features hereinafter described and claimed. I

' .F or an illustration of some of the forms my invention may take reference is to be hadv *toj'the accompanying drawings, in which:

-Figure 1.is a side elevational View of a form my invention may take when embodied in a so called dial set. Fig. 2 is a cross sectional view, some parts in elevation, of the apparatus taken on the line X-X of Fig. 3. Fig. 3 is a bottomplan view of the apparatus shown in Fig. 1. Fig. 4 is a perspec` tive view, on larger scale, of an element of the apparatus shown in Fig. 1. Fig 5 is a perspective view of one of the contact ele` ments of the apparatus illustrated in Fig` 1. Fig. 6 is a perspective view of another of the contact elements of the apparatus of Fig. 1. Fig. 7 is a plan view, partially diagrammatic, of a plug set embodying another form of my invention.

Referring first'to Figs. 1 to 6 inclusive`v a plate or block 1, of hard rubber or other suitable insulating material, mav form a support for my resistance set. Extending through the base 1 may be one or more Specification of Letters Patent.

screws 2 threading into lugs 3 upon a plate or disk 4 of suitable insulating material, preferably moldable insulating material l patented July 2s, 1914.

Application lcd March 12, 1913. Serial No` 753,694.

such, for example, as a condensation product. The plate 4 has the central hub or boss 5 which, when the lscrews 2 ,are drawn up tight thrusts with its Aupper end against the plate orv sheet 6 of insulatingmaterial between' which and the base is thereby'.

clamped or held the disk-or'plate 7.01? con` ducting material.. And between the plate* or disk v4 and the member '6 are 'held the various resistance coils A, B, C, D, and E, which may -be double wound,'that is,non inductively, upon'insulating bushings or cylinders 8 disposed uponmetal tubes 9, being held in place between the disk 4 vandthe each' tube 9 which receives such indicated inrFg. 2.

'Molded inl or to the plate4'are the'iive' metal contact plates, 10, 11, 12, 13, andv-14'. One of these plates,"as=10, is shown in perspective in Fig. ''as having the downwardly projecting portions l--an'd outwardly extending 'prtions 10", these portions 1()a and 10b being molded within the body of the disk 4, the outer ends-of the parts 10" being then bent laterallyva's seen in Figs.' 1 and 3. The holes or recesses 10b are provided to al# low the insulating material of the disk 4 t0 extend through these holes to form a more secure anchorage for the contact plate to the disk 4. The other contact' plates 11 to 14 inclusive are similarly oonstructedrand embedded and have their terminals l1"` etc., bent over as in Fig. 3, a hole 11, similar to hole 10c of Fig. 5, being shown in Fig. 3.

The coil A may be of any suitable resistance, for example, 1 ohm, 10 ohms` 100 ohms, etc., according to the range of the resistance set. For convenience the resistance of the coil A will be considered as a unit. '.lhe coils B, C, D and E, are preferably all of equal resistance, and preferably all twice the resistance of the coil A, that is, two units. One terminal of the coil A is con nected to the metal lug 7 securedl to or integral with the plate 7, this lug 7' being bent down at right angles as shown in Figs. 1 to 4 inclusive. The other terminal'of the coil A is connected to the lug 15 secured to or preferably integral with the contact plate 16 which has the lug 17 embedded or molded in the disk 4 andforlning a connection be` 19 with a binding tween the lug 15 and the plate 16. See Fig. 6. The lug 15 lis also embedded in the disk 4 and i`s then turned laterally Vparallel to the edge of the disk 4 as indicated in Fig. 1.` The plate 16 is preferably more or less embedded in the plate 4. or may be otherwise secured thereto, leaving the outer surface of the plate 16 free for contacting purposes, as is the case with the contact plates 10 to 14 inclusive. t. l

One terminalif the coil B is connected to a lug 10b of the contact v'plate'lO while its other terminal is connected to one lug 11b of the contact plate 11; one-terminal of the coil C is connected.to.the remaining lug` 11b ofcontact plate 11, while its other terminal is connected to one lug 12b of contact plate 12; one terminal of the coil D is connected to the remaining lugv 12h of plate 12 while its remaining terminal is connected Ito one lug 13b .of plate 13; and one-terminal of the coil E .islconnected to the Vremaining lug 13" of plate ,13 while its Aother terminal is connected to one lug 14b .of the contact plate 14. The remaining lug 14b of the plate 14 forms one terminal ofthe instrument which may be connected by conductor 18 to a suitable binding post terminal of the instrument. The other terminal of the instrument is the lugr 15 which may be connected by conductor post :terminal of thc instrument.`

A head-or handle-20. is secured to the shaft 21 which extends through Vthe base 1, boss 5 and disk 4, .and in sodoing passing I through the hole 7 in disk 7 and the hole 16a in the plate 16, the hole 16al being suitably larger than the shaft 21 to prevent electrical contact between plate 16 and the shaft 21. -Below the shoulder 21l of the shaft 21 is a metallic collar 22 sweated, soldered. brazed, or otherwise electrically connected to the shaft 21, the lower face of the collar 22 maintaining a firm rubbing contact with the plate 7. The firmness or perfection of this rubbing contact is further insured by the spring contact 23 formed of a plurality of laminae of resilient conducting material such as phosphor bronze, the ends of the laminzc being turned at right angles as indicated at 24 and 25 for engaging with cooperating contacts. This structure forms a relatively stiff spring which draws the collar 22 snugly against the plate 7. The brush contact 23 is secured upon the lower angular or non` circular end 21b of the Shaft 21, the laminae of the brush 23 having perforations which fit the part 21' so as to be rotated thereby, as hereafter described. A pin 21c passes through the end 2lb and retains the brush 23 in place. At approximately the center of the brush 23 it has downwardly extending laminee lugs 23a which are soldered to the conducting plate 23b which is in turn soldered to the lower end of the part 21b of the shaft 2l, whereby all the lamin of the brush 23 are in permanent and perfect electrical communication with the shaft 21 and through the collar 22 with the plate T and therefore with the lug 7 and one terminal of the coil A.

The ends of the lamina: of brush 23 are adapted to engage and traverse the metallic Contact plates 1() to 14 inclusive. The ends 25 of the laminzc of brush 23 do not extend out so far from the shaft 21 and never engage these contact plates 10 to 14 inclusive, but engage in succession.v as the shaft 21 is rotated by handle 20, the projections or raised portions 26 of insulating material integral with the disk 4, and the outwardly extending conducting projections 2T, 28, 29, 30 and 31 integral with the plate 16, these projections 27 to 31 inclusive lying between the projections 26. lt is preferred that the insulating material be cut away or depressed between the projections 26 and the neighboring contact members 2T to 31 inclusive, as indicated at 32, so that as the ends 25 of the brush 23 pass over the contacts 27 to 31 inclusive and the raised insulating portions 26 no conducting path, even of high resistance, can be improperly formed, as might be the Case by the wearing away of the material of the ends 25 upon insulating material after considerable use.

Movable with the handle 20 and shaft 21 may be a dial plate 32a which may have 10 equally spaced perforatioiis or depressions 33 in which may engage a ball or other detent 34, pressed by spring 35, the ball and spring being located in a hole 36 in the base 1. The depressions or perforations 33 are so located that the 10 different positions of th(` brush 23 may be determined. The dial plate 32"l may carry on its upper surface figures or characters, one at cach position, designating the resistance in circuit for each position, a suitable stationary indicating member 3T being provided to aid in the reading; that is, whatever ligure or character is adjacent to the stationary pointer 37 indicates the amount of resistance in the circuit.

The operati-'in is as follows: 1t being remembered that one terminal of the unit coil A is connected :he elip or tongue T', it is evident that one terminal of the coil A is permanently in electrical communication with the brush contact 23 through plate 7, collar 22 and shaft 21; and it being reinembered that one terminal of the instrument is in etl'cct the plate 16 and therefore any of the contacts 2T to 31 inclusive, while the remaining terminal of the instrument is in etl'ect contact plate 14, if the brush 23 is rotated to such position that the end 24 of the brush is in engagement with the contact plate 14 while the end 25 is engaging contact 29 of the plate 16, there is no resistance in circuit because, as will be seen from Fig.

3, current will enter, for-.example `by con'- ductor 19,. pass throughflug 15, plate 16, contact 29, brush 23, to plate 14, lug 14", and thence by conductor '18. ,-Ifnow the brush 23-be'rotated in a counter-clockwise direction, asfvievved inlFig..3, a tenth of va revolution, from ,the position above assumed, contact 24 ,ofbrush 23 will stillbein engagement with contact-14but theend y25 will be upon that insulating surface26 located between contact 29 and contact-28. lIn such case current entering by conductor19, for e.Xlllplf,,cannot-` ass to brush 23V because the end 25.is o n' ins atin material 26. It will therefore be compelled to pass through coil Ato the tongue@1 ,tothe brush `23 to plate 14 and'. to conductor 18, thus including only the coil A in circuit-j A further tentli ,of a revolution in counter-clockwise direction on the part of brush 235will bring the brush 23 tothe position illustrated in F ig. 3 in which casezcurrententerin' through conductor 19 Willpass through pate 16,.contact 28, contact 25, brush523, contact 24, to contact plate 13thence through coil l E'toY plate 14 and thence by conduct-or 18, thus including only the4 coil Ein circuit. A further` tenth of a revolution the: same direction will bring contact 25,5Jonto that insulating section 26 lying betweenl contacts .2 8 and 27, contact 24 beingstill in engagement with plate 13. In

thiscasecurrent entering by conductor 19l isagainfcomp'elledto .traverse coil A and thence ,through thel shaft' 21 and brush 23 to.A plate 13 thence through coil lE to-plate 14 and.A ,thence by :conductor l, 18, thus including both coils A and Ev in circuit in series with eachother. A ,iurther tenth of a revolution of the gbrush 23'carries its contact 25 onto contact 27 and its contact 24 onto plate 12 in which case current entering by conductor 19 Apasses ,through plate 16, contact 27, brush 23 to plate 12 thence through coil D to plate 13,1thenceV through coil E to plate 14 and thence by conductor 18, thus including in circuit only coils E and D in seriesV with each other, coil A being out of circuit. And so on for each tenth of a revolution, the coil A is alternately cut into and cut out of circuit, being cut into circuit in the position after that in which one of the coils B, C, D, or E is brought into circuit, and being cut out of circuit at each position in which a new coil B, C, D or E is brought into circuit. From `this operation it Will be seen that first a coil of unit resistance is brought into circuit, then it is cut out of circuit and a coil of doubleV unit resistance is brought into circuit; then the coil of double unit resistance is leftv in circuit and the coil ot unit resist-ance is added to the circuit, and so on. And it is apparent that by this arrangement with only five coils ten diilerent amounts of resistance may be brought into circuit varying from `zero resistance to nine units.

` And 'accordingly Wheneverthepcontact 25 of brush 23 is on any of the contacts 27to 31 inclusive the unit coil A is cut out of circuit; and Whenever` the contact 25 is on an insulatinfr-surface 26 coil A is cut into circuit.` @It will be noted further that. the structure disclosed is such as to dispense With and avoid .the errors due to connecting or cross-connecting wireswithin i the instrument, since the terminals of the coils are solderedv directly to nearfmetallic-fparts, thus requiring no connectorsnuAnd it rwill be Vobserved that betweenf'the terminals 18 and 19 of the instrument the number of rubghing or ,slidingry contacts? is constant,A namely two; part of the time these Itworubbing or sliding contacts are at .thecontacts .24 and `25 of the brush 23, and in' fthegother positions at :contact'24 of ibrush23iafndmttthe contact'ibetWeen-the collar j22; and plate 7. any error ,inf iresistance' arises from variations.-of-these=contact ,resistances. rather than-fromftheir iactual' value. Butfby the construction shown the value.;of these contact resistances is sub stantiallyV negligible and the variations of these-Icontact resistances are va minimum. Obviously the movable conticlnember 23 may be stationary and thelcont-acts 105to ,.15

`inclusive and the contacts i2` to 31--inclusive may be movable..' f M.: .,1-

,Myxinvention may. .also take. the form.r illustrated in ,-Fig. 47 whichrillustrates a plug-set# the example illustrated being; for adecade set of fourrows, that is, units, tens, hundreds, andl thousands of ohms. Upon the box cover or base 40 of hard rubber oriother suitable insulating material is provided, for the unit row, tive conducting blocks 41, 42, 43, 44 and 45 @disposed bctween two conducting bars 46 and 47. Into the holes as 48, two such holes being provided between each block and the bars, may be inserted a ,metallic plug P to form electrical communication between the block and bar. A .unit resistance 49, for example 1 ohm, has its terminals connected to the bars 46 and 47 The block 41 may be considered one terminal of the instrument or of the unit row while the other terminal of the row is bar 47, conductor 50 extending from the block 41 to the binding post or external circuit while conductor 51 connects one terminal of the resistance 49 with the block 47 and may lead to a binding post or the external circuit for cases Where the first row only is used. A second resistance 52, for-example of tivo units of resistance, has one terminal connected to 'block 41 and its other terminal to the block 42; a third resistance 53, for example equal to resistance 52, hasone terminal connected to the block 42 and its other terminal connected to the block 43; afourth resistance 54, for example equal to resistance 52, has one ter- ,rninal connected to block 43 and its other terminal to the block 44', and a fifth resistance, for example equal to resistance 52, has its one terminal connected to block 44 and its other terminal to the block 45. Assuming this la unit row, resistance 49 may be one' ohm, while each of resistances 52 to 55 is two ohms. It will accordingly be seen that by inserting the plug P between block 41 and bar 47 there willbe no re` sistance in4 circuit.' By transferring the plug P to connect'bar-41 with'b'ar 46, cur` rent will1ente'r forexample through conductor 50 'pass through block 41, plug P, bar '46through resistance 49 to conductor 51, Vthus inserting in circuit one ohm.l If now the plug be inserted between block 42 andbar -47only coil 52`will be in circuit, therefore introducing two ohms. By transferring the 'plug to 'connecty block 42 with bar'46l both resistances 49` and 52 will be in circuit in vseries with 'each' other, thus introducing threeohnis'.v And soon by insertingv the plug P in the different holes any' amountoflresi'stanc'eifrom zero to nine ohms may' be brought into circuit, by one ohm steps, inalternate Vpositions unit resistance 49 4'beix'ig excluded from the circuit. And for-the second row a unit resistance 56,1o forexample tenohms, has one terminal connected to the bar l57. And between the aeghborngblocks 5,8 `to 62. inclusive are connected double unit coils 63 to 66 inclusive' of tay'QO-'ohps each. f 'And for the third 'row 'a unitreslstance 67, of say 100=ohms, has its ohetterminal connected to the bar 68 'and its other' terminal to the bar 69JffAnd 'thelblocks 70 to 74 inclusive have connected betweerithem the resistance coils 75 to '78 linclusive leach of 200 ohms, for example. `Tlreblocks 58 and A70 are electrically connected with each other by conductor 79.' And for the fourth row a unit resistance 80, of1000 ohms, for example, has 4one terminal connected to the bar 69 and its other terminal to the bar 81. And the blocks 82 to '86 inclusive have connected -between them the resistance coils 87 to 90 inclusive each of 2000 ohms resistance, for example. And to the block 82 is connected the circuit conductor 91.

From ithe description of the first or unit row it will be apparent'that by insertingr a plug in the proper hole of each row, any resistance, from zero, varying by steps of one ohm, may be brought into circuit, a maximum resistance with the values assumed, being 9999 ohms. And as to the second, third and fourth rows, the same is true as of the first row, namely that ten different resistance values, from zero to nine units, in each row, may be obtained with only five coils. A v

It will be understood that in place 4oi? resistances herein described, may be used any other electrical units or quantities, as,

'for example, sources of current or electromotivc-forcc, capacities or condensers, or inductances.

What I claim is:

1. The combination with a plurality of resistances, stationary contacts between which some of said resistances are connected, opposing contacts, and a movable contact permanently connected to another of said resistances, movement of said movable contact with respect to said stationary contacts bringing into circuit one after another of said first named resistances, and in positions between introduction of successiveof said first named resistances bringing into circuit said last named resistance.

2. The combination with a row yof separated contacts, of resistances connected to said contacts, opposite to each of said contacts a contact and an insulator, a movable Contact member adapted to traverse said contacts and insulators in succession, and a resistance associated with said movable contact member and brought thereby into circuit when engaging only one of said first named contacts and taken out of circuit when simultaneously engaging one of said first named contacts and an opposed contact.

3. The combination with a series of contacts, resistances connected thereto, opposed separated contacts connected to each other, a movable contact adapted to bridge opposing contacts, a resistance having one termi- .nal connected to said movable contact and its other terminal connected to said inter-connected opposing contacts, said movable contact member maintaining contact with each of said first named contacts when in position intermediate neighboring of said opposing contacts.

4. The combination with a block of insulating material, of a contact having a coutact surface external to said material, a pro-` jection thereon molded in said insulating material and projecting outside of said insulating material to form an external terminal.

5. The combination with a block of insulating material, of a contact, a projection thereon molded in said insulating material and projecting from said insulating material to form a terminal, said project-ion having an aperture into which said insulating material extends.

(l. The combination with a block ot insulating material, of a contact plate threon, a projection on said contact plate molded in said material, and a lug on said projection molded in said material and projectingtherefrom to form a terminal for said plate.

7. Inaresistance scha single unit resistance` a series of double unit resistances, a series of contacts between which said double unit resistances are connected, an opposing series of inter-connected contacts, and a movable contact connected to said single unit resistance, said movable contact having two positions for each ot said first named contacts, in one of said positions said first named resistance included in circuit and in the other of said positions excluded from circuit.

8. The combination with a rotatable contact member, of a plurality of resistance coils disposed around the axis of rotation of said contact member, a plate of insulating material, a plurality of contacts having parts molded therein and projecting therefrom, terminals of said resistance coils Connected directly to said projecting parts of said contacts, another contact disposed about the axis of rotation of said rotatable contact member, said rotatable contact making and breaking circuit with said last named contact in traversing each of said plurality of contacts 9. The combination with a plurality of resistances, of relatively movable contacts, connections whereby for all positions of said relatively movable contacts the number of contact resistances in circuit is constant, and connections whereby relative movement of said contacts in every alternate position cuts out of circuit one of said resistances and in the remaining positions bringing said resistance into circuit alone or with one or more of the remainder of said resistances.

10. The combination with a plurality of resistances, of relatively movable contacts, connections whereby for all positions of said relatively movable contacts the number of contact resistances in circuit is constant, and connections whereby relative movement of said contacts in every alternate position short circuits one of said resistances and in the remaining position bringing said resistance into circuit alone or with one or more of the remainder of said resistances.

11. The combination with a plurality of resistances, of relatively movable contacts. connections whereby for all positions of said relatively7 movable contacts the number of Contact resistances in circuit is constant, said relatively movable contacts comprising two series of contacts and a movable contact, said movable Contact in two neighboring positions connecting contacts of the two series together and engaging the same contact of the one series alone.

12. The combination with a plurality of resistances, of relatively movable contacts, connections whereby for all positions of said relatively movable contacts the number of contact resistances in circuit is constant, said relatively movable contacts comprising two series of contacts and a movable contact, said movable contact in two neighboring positions connecting contacts of the two series together and engaging the same contact of the one series alone, and connections whereby in each alternate position of said movable contact one of said resistances is cut out of circuit and in every other position said resistance is brought into circuit alone or with one or more of the remainder of said resistances.

13. The combination with a plurality of resistances, of relatively movable contacts, said relatively movable contacts comprising two series of contacts and a movable contact, the contacts of one of said series interconnected with each other through connections of negligible resistance, said movable contact in two neighboring positions connecting contacts of the two series together and engaging the same contact of the one series alone. l

14. The combination with a plurality of resistances, of relatively movable contacts, said relatively movable contacts comprising two series of contacts and a movable contact, said movable contact in two neighboring positions connecting contacts of the two series together and engaging the same oontact of the one series alone, and connections whereby in each alternate position of said movable contact one of said resistances is cut out of circuit and in every other position said resistance is brought into circuit alone or with one or more of the remainder of said resistances.

15. The combination with a series of contacts, of a plurality of resistances connected between said contacts, a. conducting member having a plurality of contacts, and a movable contact member which in neighboring positions connects a contact of said series with a contact of said conducting member and connects with the same contact of said series alone.

16. The combination with a series of contacts, of a plurality of resistances connected between said contacts, a conducting member having a plurality of contacts, a movable contact member which in neighboring Ositions connects a contact of said series with a contact of said conducting member and connects with the same contact of said series alone, and a resistance whose terminals are connected respectively to said movable contact and to said conducting member.

In testimony whereof I have hereunto affixed my signature in the presence of two subscribing witnesses.

IRVING B. SMITH.

iVitnesses:

NELLLE EVANS, ALICE S. MARSH.

Copies of this patent may be obtained for tive cents cach, by' addressing the Commissioner of Patents, Washington, D. 6i" 

